Well, then, Step Three: catch Catwoman, recover the opal, then come back for Harley Quinn! 
- — Batgirl
Scooby-Doo! Team-Up #12 is an issue of the series Scooby-Doo! Team-Up (Volume 1) with a cover date of November, 2015. It was published on September 23, 2015.
Synopsis for "Gotham Ghouls"
This story is reprinted from Scooby-Doo! Team-Up #23.
Mystery, Inc. have arrived at Gotham City. A unsigned message told them to come there and wait on a rooftop at night. Daphne and Fred think it has to be a call from Batman, but it is Harley Quinn and Poison Ivy who turn up. The whole team turns around to run away, but Poison Ivy's vines trip them.
Harley explains they're being haunted and invites them in their -surprisingly nice- apartment. Reluctantly, the Gang listens to their story: a couple of weeks ago, Harley and Ivy -hypothetically- stole the ancient Opal of Osiris, and the -hypothetical- Opal must be -hypothetically- cursed because ever since then, something goes wrong every time they try to steal stuff: alarms, armed guards, conga lines, sprinkler systems...
Velma suggests just to give it back, which both villains refuse to do. All of sudden, a spectral robed figure appears in the room, stating they will hand over the Opal to him if they want to be free of the curse. Both the gang and the villain duo run away again and hide behind Ivy's giant plants. Nonetheless, the ghost is already gone.
The Gang take a quick look around, wich provides no clues. Ivy feels suspicious and points out it's awfully coincidental that ghost showed up right in their home at the same time the kids did. Shaggy babbles that they'd never work with a ghost, they don't know anything and he definitely needs a super-hero now. Right then the ghost appears again, and Shaggy feels relieved, thinking it must be Batman following his clue. Shaggy happily pulls the figure's cowl down, revealing not Batman but Catwoman.
This story is reprinted from Scooby-Doo! Team-Up #24.
Catwoman dressed up as a ghost because she thought she could skip the obligatory fight if she scared Harley and Ivy into handing over the Opal of Osiris, which they stole before she had the chance to do so. Harley wonders why Catwoman claims it should be hers, and Velma points out it must be a cat's-eye opal.
Regardless, Harley refuses to hand over the Opal. Still, Catwoman quickly finds it and leaps her way to the nearest exist, only to be stopped by Ivy's coiling cattails. Catwoman quickly shreds Ivy's plants and dodges Harley's hammer blows.
The Scooby Gang rushes towards the door while they fight, but Harley gets in their way. Suddenly another robed ghost appears, demanding the opal. They all decide to run. In the ensuing chaos, Daphne is nearly crushed down Harley's mallet when Scooby accidentally trips the villain. The red-headed detective gets mad. Sick of that argument over something doesn't even belong to any of those villains, she snatches the Opal from Catwoman's hands and tosses the gem to the ghost.
The ghost takes off her robe and reveals her true identity: Batgirl. Batgirl quickly freezes Ivy with liquid nitrogen pellets, but Catwoman snatches the gem back and runs away. Batgirl and the Scooby-Gang chase after her.
Harley hurries after them. She barges into a room and finds Catwoman tied up and Velma leaning over a redhead. Harley believes her to be Batgirl and gets ready to flatten her, but the girl turns around and Harley realizes it's Daphne. Behind her, Batgirl snatches her mallet and smashes her down.
Soon the three villains are tied up and Batgirl is ready to turn them over to the cops and return the opal. Batgirl praises Daphne by her bravery in playing decoy, but Fred wonders why Daphne gave the opal to the ghost before they knew she was Batgirl. Daphne explains she realized the first ghost was wearing black gloves under the robes, but the second one wore yellow gloves. As far as she knows, there's only one costumed Gothamite vigilante who wears yellow gloves.
Batgirl and Daphne high five each other, ignoring Ivy's grumblings caused by Daphne's statement that redheads have to stick together.
Fred thinks they're lucky that Batgirl showed up, but Batgirl contradicts him. It wasn't luck. As Velma pretended to search the room, she tied the curtains together to improvise a makeshift Bat-Signal.
Shaggy makes a pun which gets Harley groaning. At least, she thinks, the Joker's jokes are actually funny.
Appearing in "Gotham Ghouls"
Featured Characters:
- Mystery, Inc.
- Batgirl (First appearance)
Supporting Characters:
Villains:
- Catwoman (First appearance)
- Harley Quinn (First appearance)
- Poison Ivy (First appearance)
Other Characters:
- Ace the Bat-Hound (Mentioned only)
- Batman (Mentioned only)
- Robin (Mentioned only)
- The Joker (Mentioned only)
Locations:
Items:
Vehicles: